The invention resides in an improved analytical method for determining hydrogen form acids and hydroxide form bases in the presence of salt interferences.
More specifically, the present invention resides in a flow injection method for determining acid or base species concentrations in the presence of salt, comprising the steps of injecting sample into an aqueous carrier, analyzing the sample in carrier solution and storing the resulting signal thereby generated, said signal being proportionate to the acid/salt or base/salt concentration of the sample, eluting the sample in carrier through an ion-exchanger effective to derivatize the acid or base species to water or absorb the acid species, and to derivatize the salt in whole or in part to a soluble hydroxide derivative or soluble hydrogen derivative, respectively, said elution step being carried out for acids in a basic ion-exchanger in the hydroxide ion form and/or free amine form and for bases in an acidic ion-exchanger in the hydrogen ion form, analyzing the effluent of the ion-exchanger to obtain a calibrated signal which is proportionate to the original salt concentration, and establishing the difference in signals to determine the acid or base species concentration in the original sample.